A graphic means of representing deductive proofs in a sentential system of symbolic logic is presented. Proof construction is characterized as a domain of the cognitive theory of problem solving, and three different interface designs for supporting the working backwards method of proof construction are demonstrated. Following a description of the rule set and the working backwards method, an analysis is given of student performance data that has guided interface development during the past two years. One interface design is shown to be superior to the others in respect to working backwards. Finally, some general conclusions are drawn concerning the relevance of instructional programs for empirically documenting student difficulties and for improving interface designs.